Electron discharge device



April 25, 1933. J. w. MARDEN 1,905,035

ELECTRON DISCHARGE DEVICE I Filed Feb. 25, 1929 luv 3 1T zz INVENTORd.W.M

ATTORNEY Patented Apr. 25, 1933 UNITED STATES PATENT- OFFICE JOHN 'W.MABDEN, 01' EAST ORANGE, NEW JERSEY, ABSIGNOB TO WESTIN'G HOUIE LAMPCOMPANY, A. CORPORATION OF PENNSYLVANIA.

ELEGIBON DISCHARGE DEVICE Application nice February as, 1929. Serial30.84%,7871

This invention relates to an electron discharge device and morearticularly to such device of the type in w 'ch the cathode 1s heatedindirectly by a heating element disposed adjacent thereto.

One of the objects of the present invention is to produce an electrodestructure employing such an indirectly heated cathode, wh1ch is com actand rugged and in which the parts t ereof are easy to manufacture andassemble.

Another object is to roduce a cathode adapted to be heated in irectly bya separate heating element in which the cathode is quickly heated tooperating temperature when heating current is applied to the heatingelement.

Another object is to provide a tube of the above nature in which theheater leads will be short and in which alternating heating current,flowing in the leads will produce a minimum of interference with theother electrode.

Other objects and advantages will hereinafter appear.

In accordance with my invention, I form the cathode into an inverted cupshape, dome shape or similar shape having a closed top and side wallsand an open bottom, and I mount the cathode on a disc of 1 nsulat1ngmaterial, such as lava rock, thoria, porcelain, etc., which closes thebottom opening of the cathode. The heating element for the cathode ismounted upon the insulating disc, preferably out of contact therewithand serves to heat the cathode, entirely by radiation. The controlelectrode and anode are of similar shape to the cathode and are nestedin proper spaced concentric relation to the cathode.

The electrode assembly is relatively short, projecting only a smalldistance above the stem of the tube whereby a rigid mount is produced,substantially free from microphonic efi'ects.

In order that the invention may be more fully understood reference willbe had to the accompanying drawing in which,

' Fig. 1 is a side elevation ofa three electrode tube embodying myinvention, showin the electrode assembly in section. i 2 is aperspective view of the insulat- 111% c ig. 3 is a perspective view of"disc with u a heating element mounted-thereon.

Fig. 4 is a perspective view of a modified maimer of mounting theheating element, an

Fig. 5 is an elevational view of a screen 00 grid tube showing theelectrode assembly in section.

The device shown in Fig. 1 comprises the envelope 10 containing a heaterelement 11, cathode 12, control electrode or grid 13 and as an anode 14.The cathode 12 consists of a cup or cap shaped metal member havingpreferably a maximum vertical height not greater than the maximumhorizontal dimension thereof, and preferably bein comprised 10 of nickelhavin an exterior sur ace coating of alkaline eart carbonates. It issupported on a disc 15 of insulating material, which completely closesthe lower end thereof. Current is conducted to the cathode surface by awire 16 secured to a leading-in conductor 17 sealed through the press.

The insulating. disc 15 is provided with a shoulder or ledge 18on whichthe cathode rests and by which it is restricted from movement relativeto the heater element 11. The disc is provided with two apertures 19 and20 arranged respectively at the center and near the edge of the disc,through which the current conducting sup orts 21 and 22 pass. Thesupports 21 an 22 are carried by the leading-in wires 23 and 24 and havean enlargement or shoulder 25 upon which the insulator 15 rests.

The heating element 11, as shown in Figs. 1 and 3, consists of a coil orspiral of tung- 'sten having a central vertical wire portion welded tothe support 21 and a depending helical portion having its end welded tothe support wire 22. 96

Obviously the heating element'may take Y other shapes but preferably itis supported above the insulator out of contact therewith in order toavoid unnecessary heating ofthe insulator. In' Fig. 4 the heatingelementis 100 in the form of a fiat spiral 26 supported parallel to andpreferably above the surface employing an anode of about 5 mm. diameterand 5 mm. in height with the cathode and grid entirely containedtherein, tubes have been constructed having substantially the samecharacteristics as the usual form of insulator tube having a cathode ofabout 25 mm. in length. The short electrode structure may be mountedrelatively close to the press on short support wires and thus there isvery little tendency of the structure to vibrate.

In Fig. 5' the structure is modified by the inclusion of a shielding orscreening grid between the control grid and the anode. to reducecapacity effects therebet'ween. The electrode assembly comprises theheating element 26, shown also in Fig. 4, cathode 27, control grid 28,screen grid 29 and, anode 30. When employing the Hat spiral heatingelement 26, the cup shaped cathode may be made more shallow and theentire electrode assembly correspondingly shortened. I

In Fig. 5 the control grid is supported from the end of the tubeopposite the plate support by a wire. 31 sealed through the dome of thebulb. The shielding grid 29 is supported fromthe press bythe wire 32.and has 'a neck portion 33 surrounding the control grid support toshield thesame from the exterior of the anode. A'pair of insulatingspacers 34 and 35 prevent displacement of the neck portion 33 andcontact thereof with the wire 31.

\Vhile specific embodiments of the invention have been described it isto be understood that various modifications and changes may be madewithout departing from the invention and the embodiments shown anddescribed are to be considered only as illustrative of the invention andnot restrictive.

What is claimed is: v

,1. A cathode structure for an electron discharge tube comprising a discof insulating material, saiddisc having-a shoulder on the peripherythereof, a hollow cup shaped cathode, having an open end, supported onsaid disc with the open end thereof engaging saidshoulder, said dischaving a pair of apertures therein, current conductors extending throughsaid apertures and a heating element supported above said insulator bysaid conductors.

2. A cathode structure for an electron discharge tube comprising a discof insulating material, a hollow tubular cathode having a single openend, resting upon said disc, said disc rojecting a short distance intoand entire y closing the open end of said cathode current conductorsextending through said disc into said cathode and a heating elementsupported on said conductoirs out of contact with said disc and cathe.

3. An electrode assembly for an electron discharge tube comprising a.cup shaped cathode having a single open end an insulating member closing'said'open end, a heating element disposed within said cathode, a gridelectrode and an anode of substantially theplurality of nested invertedcup shaped electrodes, the smallest electrode constituting the cathode,a disc of insulating material having a shoulder engaging the open end ofsai cathode and completely closing the same, current conductorsextending through said disc and aheating element contained within saidcathode and supported out of contact with said insulating disc, by saidcurrent conductors.

6. An electron discharge tube comprising an envelope, a cup shapedcathode therein having an open end, an insulating member closing saidopen end, a heating element Within said cathode, a control electrode,screen grid and anodeof substantially'the same shape as said cathodeconcentrically disposed about. said 'cathode,.said cathode, screen gridand anode being supported from one end of said envelope and said controlelectrode being supported from the opposite end of the envelope.

In testimony whereof, I have hereunto subscribed my name this 21st dayof February 1929.

- JOHN W. MARDEN.

